Reading this thread (and others like it) makes me realise just how very lucky we are to be near our children and grandchildren. My son and his wife are only half a mile away and my daughter lives just over two miles away.
Yes it does mean that we are sitting targets for babysitting, often at the last minute when, e.g., my daughter in law is due at a meeting and my son finds he can't get home in time. But rather that than be 100's of miles away.
We moved 300 miles away from my mum when our children were 3 and 4, and now it makes me feel so sad to think of her bravely waving us goodbye. We didn't have Facebook or Skype in those days - we couldn't even afford to have the telephone connected! So I would walk to the phone box once a week and ring her, and we used to send cassette tapes of the children talking and singing and so on. No video clips though, because the cost of camcorders in those days was astronomical (and they were huge pieces of kit!!).
So yes, keeping in touch today is a hundred times better than it was, but it's never the same as being able to pop round for a cuppa and a cuddle with your grandkids, so I really feel for you all.